The present invention relates to a head gimbal assembly (HGA) with an IC (integrated circuit) chip for a thin-film magnetic head used in a magnetic hard disk drive (HDD) for example and a manufacturing method of the HGA.
In the magnetic HDD, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of the HGAs.
Recently, recording data rate in the magnetic disk rapidly increases to satisfy the requirement for ever increasing data storage capacities and densities in today""s HDDs. In order to achieve higher frequency recording, proposed configuration is a HGA structure with a suspension for supporting both a magnetic head slider and a drive IC chip of a driver circuit for the magnetic head element. According to this structure, since the length of trace conductors from the driver circuit to the magnetic head element can be shortened, generation of unnecessary noises from the trace conductors can be effectively suppressed resulting high frequency recording characteristics to improve.
The IC chip may be however heated to a high temperature due to the writing current flowing through itself during recording operations. In order to cool the heated IC chip by air flowing produced by the rotating magnetic disk, the IC chip will be mounted on a surface of the suspension, which counters the magnetic disk surface in operation.
The HGA with the IC chip will have a larger thickness increased by the mounting height of the IC chip. Generally, in the HDD, in order to increase the record capacity per magnetic disk, both sides of the disk are used for recording, and in addition, a plurality of the magnetic disks are axially mounted. Therefore, two HGAs for writing/reading magnetic information will exist between the two magnetic disks, and thus the whole thickness of the magnetic disk device equipped with the HGAs with IC chips becomes great. This large thickness of the magnetic disk device will become a big problem particularly when the magnetic disk device is mounted in a thin notebook type personal computer.
Therefore, it is required for such an IC chip to be fabricated thinner than a general-purpose IC chip. Namely, the general-purpose IC chip has a thickness of about 0.3-0.4 mm, whereas the IC chip for the thin-film magnetic head has a thickness less than 0.25 mm, for example a thickness of about 0.12 mm.
The C4 (Controlled Collapse Chip Connection) process is a typical process for mounting such an IC chip on a suspension. In the C4 process, first, flux for solder material is applied to bump balls of the IC chip and then the IC chip is bonded to connection pads by reflow heat bonding.
If the mounting of the IC chip is performed by the reflow soldering using flux, it is necessary to execute the cleaning process after bonding. Namely, in the C4 bonding process, flux is applied to bumps on the IC chip surface, in order to promote melting of the solder and temporarily adhere the IC chip to the suspension during reflow soldering. Since the applied flux may have adverse effect of producing out gas for example, the cleaning has to be done after bonding.
This cleaning process will exert an influence upon the suspension. Namely, although high accuracy is required in a bending angle of the suspension, this bending angle may unintentionally change during the cleaning process. Thus, it is difficult to use the C4 process in the mounting of the IC chip on the suspension.
An ultrasonic bonding can be carried out without executing the cleaning process. In the ultrasonic bonding process, no solder bump is used but gold (Au) bumps formed on the IC chip are used. Namely, bonding is executed by applying an appropriate pressure and ultrasonic vibration to the Au bumps that are contacting with the respective Au pads on the suspension so as to be active Au for bonding. Since no soldering flux is utilized in this ultrasonic bonding process, cleaning process is not necessary used.
However, if the IC chip is caught with strong force by an ultrasonic bonding head and a heavy load and great ultrasonic power are applied from the bonding head to this very thin and small IC chip in order to mount it in the ultrasonic bonding process, damages such as scratches or cracks may be produced on the IC chip back surface.
If a few damages such as scratches or cracks arise on the IC chip surface, a silicon particle falling from this IC chip may occur. This is never allowed in the HDD. Namely, in the HDD, generally, since the magnetic head slider flies at extremely low height above the rotating disk for performing reading/writing operations, no dust is allowed to exist.
It is therefore an object of the present invention to provide a HGA with an IC chip and a manufacturing method of the HGA whereby no falling particles from the IC chip will occur.
According to the present invention, a HGA includes a magnetic head slider having at least one thin-film magnetic head element, an IC chip having a circuit for the at least one thin-film magnetic head element, and a suspension for supporting the magnetic head slider and the IC chip. All surfaces of the IC chip are coated by additional insulation layers.
Since all surfaces of the IC chip are coated by the additional insulation layers, chippings produced on the IC chip due to dicing of the IC chip from a wafer and/or damages such as scratches or cracks produced on the IC chip back surface due to catching by the ultrasonic bonding head when mounting the IC chip will be wholly covered by the additional insulation layers. Thus, particle falling from the IC chip can be completely prevented from occurring. Furthermore, cracks on the IC chip can be prevented from being produced even when a certain shock is applied to the IC chip after mounting.
It is preferred that the additional insulation layers include an underfill layer filled in a standoff between the IC chip and the suspension. Also, it is preferred that the additional insulation layers include an insulation coating layer for covering a top surface and side surfaces of the IC chip.
The underfill layer and the insulation coating layer may be formed by the same insulation material, or by different insulation materials.
It is preferred that the additional insulation layers are made of a material containing a resin material. Preferably, the additional insulation layers are made of a mixture of a resin material and an insulation material with high heat conductivity.
It is also preferred that the additional insulation layers are made of a material with a viscosity of 0.5-80 Paxc2x7s at the room temperature (25xc2x0 C.). If the viscosity of the filling and coating insulation materials is kept within this range, the thickness of the HGA will not so increase due to the additional insulation layers covering all the surfaces of the IC chip.
According to the present invention, also, a method for manufacturing a HGA includes a first step of mounting a magnetic head slider having at least one thin-film magnetic head element and an IC chip having a circuit for the at least one thin-film magnetic head element on a suspension, a second step of filling a first insulation material into a clearance between the IC chip and the suspension, and a third step of coating a second insulation layer onto a top surface and side surfaces of the IC chip.
It is preferred that the first and second insulation materials are formed by the same insulation material, or by different insulation materials.
It is preferred that the first and second insulation materials are made of a material containing a resin material. Preferably, the first and second insulation materials are made of a mixture of a resin material and an insulation material with high heat conductivity.
It is further preferred that the second step includes dispensing at least one drop of the first insulation material in liquid state from a needle onto the suspension near the IC chip to fill the first insulation material into the clearance between the IC chip and the suspension.
Preferably, third step includes dispensing at least one drop of the second insulation material in liquid state from a needle onto a center portion of the top surface of the IC chip so that the top surface and the side surfaces of the IC chip are coated by the second insulation material.
Also, preferably, the third step includes dispensing drops of the second insulation material in liquid state from a needle scanning over the top surface of the IC chip so that the top surface and the side surfaces of the IC chip are coated by the second insulation material.
It is preferred that the additional insulation layers are made of a material with a viscosity of 0.5-80 Paxc2x7s at the room temperature (25xc2x0 C.). If the viscosity of the filling and coating insulation materials is kept within this range, the thickness of the HGA will not so increase due to the additional insulation layers covering all the surfaces of the IC chip.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.